Biosynthesis of the Peptidoglycan of Bacterial Cell Walls

Abstract

Abstract d-Alanine carboxypeptidase I, which removes the terminal d-alanine residue of the uridine nucleotide, UDP-N-acetylmuramyl pentapeptide, and several related compounds occurs in both the particulate and soluble fractions of Escherichia coli and several other gram-negative bacteria. The soluble enzyme has been purified 120-fold and some of its properties are reported. The enzyme is competitively inhibited by penicillins and cephalosporins at very low concentrations. d-Alanine carboxypeptidase II, which catalyzes the hydrolysis of the penultimate d-alanine residue of the uridine nucleotide substrate, has also been purified and separated from d-alanine carboxypeptidase I. This enzyme is not inhibited by penicillins and cephalosporins. The possible physiological substrate and function of these enzymes are discussed.